In the first instance, are the AU plugs in the menu .components or .auinfo?
If the latter, then It may well be that the file path that has been 'remembered' and therefore loads at first, is the file path to the auinfo folder on my hard drive, which of course wont be a vaild file path on yours.
If you click the 'Set Auinfo' folder' button and navigate to your ~/Users/Library/Application Support/VSTShell Preferences/Components folder, you should find things load as expected.
Unfortunately this cannot be set automatically, as it depends on specifying a file path in your user account.
To safeguard against this, the default was meant to be your system library..../Audio/Plug-ins/Components folder, but it looks like that is not happening.

In the second case, are you in Safe Load mode, or if not, are the Load Enable buttons for the slots lit?
The whole Safe Load thing is not yet how I'd like it to be, but without it, preset recall can be dodgy, and that's what folks asked for.
I will look at sorting it out, but in the meantime I think it's largely a matter of thonking of loading aplug as being a two-click process - select in the menu, then click the load button - in fact it may be easier if I just make that the only, option.

Let me know if this helps, and I'll see what I can do if not,
Cheers
Roger

It was a little confusing, but I've figured out what's happening. After pointing to all the correct folders and refreshing, I have to select from the "*.auinfo" files to play the sub-components of the AU component files. But on a restart, after MIDI, DSP, and VSTi status are enabled, even though the VSTi-selector opens to the correct auinfo folder and allows selection of an auinfo softsynth, no sound occurs and no GUI shows (when "Edit" is clicked) unless I refresh the location by using "Set AUinfo folder" and click on "Open". This resets the softsynth selector and when the same auinfo component first selected is re-selected, it now plays and its GUI opens when "Edit" is clicked. It seems like something in VSTShell is forgetting the location of the auinfo folder.

On my system, the "Library" folder in "Users" is a hidden folder and accessing it from the VSTShell "Open" view required the use of CMD+Shift+G and a manual entry of the folder path. It was otherwise inaccessible.

The FX mixer is very functional with pre/post and seems to be working for most plugins. However, I don't know why but I got massive feedback using some of the U-he Uhbik processors (with Ubhik-A it was almost immediate, and Uhbik-D took longer by playing with the controls but also was bad; both did nothing at first when instantiated). It didn't matter if the effect channel was in pre or post. Something must be odd with the routing with those; these plugins are 5.1 capable and from the GUIs it looks like they're defaulting to a surround configuration... perhaps I/O isn't being specified properly?